Loans - Unpaid Principal Balances by Delinquency Status (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2023	Dec. 31, 2022
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	$ 9,130,933	$ 9,130,933	$ 9,008,979
Nonaccrual loans	63,866	63,866	78,965
Total loans	10,977,162	10,977,162	10,549,845
Nonaccrual loans with no associated allowance	23,800	23,800	22,000
Interest received on nonaccrual loans	400	1,900	5,600
Farm & Ranch
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	6,410,672	6,410,672	6,362,326
Nonaccrual loans	63,866	63,866	63,402
Total loans	6,410,672	6,410,672	6,362,326
Corporate AgFinance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	1,223,777	1,223,777	1,166,253
Nonaccrual loans	0	0	15,563
Total loans	1,223,777	1,223,777	1,166,253
Agricultural Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual loans	63,866	63,866	78,965
Total loans	7,634,449	7,634,449	7,528,579
Rural Infrastructure Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	3,342,713	3,342,713	3,021,266
Nonaccrual loans	0	0	0
Total loans	3,342,713	3,342,713	3,021,266
Current
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	10,885,584	10,885,584	10,459,282
Current | Farm & Ranch
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	6,319,094	6,319,094	6,287,326
Current | Corporate AgFinance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	1,223,777	1,223,777	1,150,690
Current | Agricultural Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	7,542,871	7,542,871	7,438,016
Current | Rural Infrastructure Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	3,342,713	3,342,713	3,021,266
Total Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	27,712	27,712	11,598
Total Past Due | Farm & Ranch
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	27,712	27,712	11,598
Total Past Due | Corporate AgFinance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	0	0	0
Total Past Due | Agricultural Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	27,712	27,712	11,598
Total Past Due | Rural Infrastructure Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	0	0	0
30-59 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	15,652	15,652	10,066
30-59 Days | Farm & Ranch
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	15,652	15,652	10,066
30-59 Days | Corporate AgFinance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	0	0	0
30-59 Days | Agricultural Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	15,652	15,652	10,066
30-59 Days | Rural Infrastructure Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	0	0	0
60-89 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	5,321	5,321	392
60-89 Days | Farm & Ranch
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	5,321	5,321	392
60-89 Days | Corporate AgFinance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	0	0	0
60-89 Days | Agricultural Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	5,321	5,321	392
60-89 Days | Rural Infrastructure Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	0	0	0
90 Days and Greater
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	6,739	6,739	1,140
90 Days and Greater | Farm & Ranch
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	6,739	6,739	1,140
90 Days and Greater | Corporate AgFinance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	0	0	0
90 Days and Greater | Agricultural Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	6,739	6,739	1,140
90 Days and Greater | Rural Infrastructure Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	$ 0	$ 0	$ 0